1988 custom cruiser rebuild

CustomCruiser

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Nov 18, 2020
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My sons and I are rebuilding a 1988 custom cruiser. What models and years can I source a stronger rear axle assembly from? Other than custom or aftermarket what are my options for trans crossmembers when installing a 4l60 or 4l80? We have a 5.3 ready, we need help deciding what drivetrain parts to install to withstand the increased power. Thanks in advance.
 

Shortfuse

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May 15, 2020
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The stock rear axle in that should be plenty strong with the addition of a locker of some sort. Unless you are going for a really high output setup there is no need to change it. The wagons came with the largest axles availible from gm for passenger car use already unless you where to switch to a 12 bolt setup that is really not nessecary spend you r money else where. I have been turn wrenches for a living for 33 years and and abusing b body axles for 25 of those years. Unless you are going to drag race it or are making over 500hp leave it be. Now if you really want to change it Strange axle company can set you up with a package for a few grand of either a upgraded gm of ford 9 inch that will be made to custom fit your ride.
 

CustomCruiser

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Nov 18, 2020
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Thanks, I was leary of that ring and pinion being that small. Its definitely worth a try, a it can do is break. Any guidance on crossmember for trans? The th200 thats in it needs work. Before I rebuild I'd rather switch to a 4l60 or 4l80 for drive ability and dependability. Thanks again, not much help out there for b bodies but we've fallen for this wagon. Its just to clean.
 

Shortfuse

Member
May 15, 2020
31
8
There are a ton of different cross members out there but I always either make my own or modifiy one. The gm 8.5 10 bolt is not weak the only breakages really occcur in drag racing when high shock loads are being forced upon them from say clutch dumps or trans break launches. I would hold off on the rear till last as the 4l60 or 4l80 will give you a much lower first gear if my memory serves me correctly so a drop in locker should be all you need unless your wagon has like a 2.32 to1 rear gear in it . Any how see how it performs before dropping a lot of cash in something you probably will not need. I have an 82 impala with a very high output 383 and a stock rear axle with locker and it has held up for 15 years of abuse and I mean abuse.
 
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GoodOldsGuy

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Oct 20, 2020
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Texas
Hi, I’m not as completely familiar with the late 80’s Custom Cruisers as earlier models so some things could be different. Many (if not all) earlier Custom Cruisers 77 and up square bodies) came with fairly durable rear axle assemblies. My 79 came with an 8.5”, limited slip posi, “P” axle that was/is plenty capable behind the 403-TH350 combo, under a 4200lb car, pulling a 4000lb trailer, geared in 2.41:1 no less. Your ‘88 may have something similar. Ring gear and pinion isn’t that hard to change if you’re looking for better off the line performance, but I don’t see a 330ci SBC blowin out my P axle assembly unless it was heavily modified.
Your transmission tunnel is large enough to accommodate even a large transmission like a TH400/4L80. The TH350/TH350C/700-R4/4L60 should fit inside the tunnel easily. I’ve attached a transmission dimension chart. It shows the placement of the mount on various models. The 200-4R that likely came stock on your ‘88 Custom Cruiser does not have a separate tail shaft housing and the trans mount is quite a bit further south than other transmissions. Move the cross member forward on the frame to line up the mount on a 700R4/4L60. You might not even need to drill any holes as the may be there already (ala TH350 applications) or order an RCB700 from Summit if you want double bumps for dual exhaust, (both of my 2 1/4” pipes go through the passenger side bump on my ‘79-not the most efficient for power, but it works) but you may still need to drill some new frame holes. I’m more concerned with the computer to make an electronic transmission (4L60E/4l80) work. You’ll need the computer from the donor vehicle to run the 5.3l/330ci AND the 4L60E it was likely paired with. I am unaware of a 5.3/330 ever being paired with a 4L80 from the factory. I’m sure there are aftermarket computers available to make a 4L80 work but I’m guessing it would take a lot of cubic dollars to do so. That said, the TH200-4R can be, and has been built to handle “big” power. (Grand Nationals came stock with them) 500 HP versions are available online, they bolt right up to your car, and require no computer, just a well adjusted TV cable (throttle valve cable-NOT a detent cable) the vacuum and transmission pressure switches that already exist on your Custom Cruiser, and it’ll work fine. Not to mention the added benefits of not having to figure out how to make your speedometer work with an electric transmission and using the driveshaft, yoke, cross member, and trans mount system that you already own. :)
I understand that the stock 5.0/307 leaves a lot to be desired in the performance department, but that can be addressed in a lot of ways including putting a 7.4l/455ci under the hood which fits in your engine compartment AND bolts directly to your frame and (well built) 200-4R. A 1969 Olds 98 came from the factory with a hi output, 10.25:1 compression ration, 360+hp, and a very impressive 500ft/lbs of torque. It won’t make a dragster out of your Dragon (as I affectionately call them) but it’ll keep your Oldsmobile an Oldsmobile and move your Custom Cruiser down the road very impressively.Just add an Oldsmobile Diesel emblem on the tail gate and you’ll have one Deluxe sleeper on your hands/under your foot. Either way, TH200-4R’s came with universal bell house bolt patterns and will bolt to any GM V8 (and most V6’s) of the era. That’s any B.O.P. (Buick/Olds/Pontiac) plus any Cadillac or Chevrolet.
You might be willing to spend a truckload of American dollars on the job, but you have lots of options with the stuff you already own. Again, if you’re looking to make a dragster out of it, disregard everything I just said, pick up the radiator cap and slide an LS3 (with the entire driveline and computer) underneath it and you’ll be halfway there. :)
 

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CustomCruiser

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Nov 18, 2020
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I understand completely and thanks for your input. I have a 5.3ls that came from another one of my vehicles. The engine and ecm are all there and have already been reprogrammed to run just the engine. I'll look at the cost of the th200 rebuild since it would make it easier. Thank you again, great info.
 

GoodOldsGuy

New member
Oct 20, 2020
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Texas
I understand completely and thanks for your input. I have a 5.3ls that came from another one of my vehicles. The engine and ecm are all there and have already been reprogrammed to run just the engine. I'll look at the cost of the th200 rebuild since it would make it easier. Thank you again, great info.
You bet :) Make sure that you specify TH200-4R and not a TH200. There are a few TH200C models (with lock up torque converters) that’ll have the electronic connector on the side. It may look like a 4 speed, but it’s not. They’re also different size than a TH200-4R. The 200-4R has a 2.74:1 1st gear. Not as low as the 3.06 in a 700R4/4L60, but plenty low anyway. 200-4R’s also gave the added benefit of a .67:1 overdrive, a little higher than the 700/4L60’s .7:1 OD. The Custom Cruiser is still a big square box at 75mph so every little bit of efficiency help counts. (Daily driver stuff). The 5.3 Chev has plenty of torque to carry a hi OD and a steep rear end (2.41ish) and will buy you a lot of efficiency on the highway. 20+mpg at 70 is not out of the realm of possibility. Do NOT run a 200-4R in OD very long without a torque converter lock up system in place, that works. It’ll overheat and lunch an expensive “plus feature”. I’m glad you’re the one figuring out the computer system. For an old guy like me, there’s not a lot I can do for ya if there’s no Quadra-bog (or even 2 of them!) on top of the engine, but I understand that you can’t pull up to a Sunoco pump and turn the knob to 105 octane leaded premium for 50 cents a gallon anymore, buy 30 of those gallons and be happy if they moved your car 250 miles. Generally in those days I’d have my foot so far into the throttle that my right shoe would be wet with gasoline when I got where I was going and I’d get Christmas cards from all the oil companies.